1. Field of the Invention
The present invention relates to a lancet assembly and, more particularly, to a lancet assembly having an injection molded housing with a metal stylet mounted therein and an injection molded removable cap or shield over the housing to protect the stylet.
2. Background Description
A lancet is a device commonly used in hospitals, doctors offices and homes to pierce a patient's flesh to draw capillary blood for diagnostic testing. Conventional lancets consist of a shank portion having at a distal end a blade or spike, which is sharp and adapted to pierce the patient's skin so to sever capillaries and provide blood for testing. Since the blade or spike is sharp, some lancets are provided with a removable shield for protectively covering the sharp edge or point of the lancet's blade or spike when not in use to protect the patient and users from inadvertent skin puncture.
There are a number of conventional lancet instruments available to aid a user in puncturing or penetrating a patient's skin to draw and sample a small outflow of blood. For example, U.S. Pat. No. 4,577,630 (Nitzsche et al), which is assigned to Becton, Dickinson and Company, shows a disposable lancet assembly for use in a reusable breach loading target pressure activated lancet firing device. The lancet assembly includes a rectangular handle portion, a lancet point extending outwardly from a distal end of the handle portion, and a removable shield adapted to mate with the lancet point when the lancet assembly is not in use to protect users from accidental puncture.
U.S. Pat. No. 4,517,978 (Levin et al.) shows another type of blood sampling instrument for drawing a blood sample from a patient's finger. The instrument described in Levin et al. includes a reusable tubular housing having a spring chamber for driving a needle held in a disposable needle holder into a patient's finger, when a trigger button on the side of the tubular housing is depressed. Prior to use, a disposable needle holder is slidably mounted in a socket within the tubular housing on a plunger member and the plunger member is slid to an armed position. The armed instrument is then placed against a patient's finger and activated using the trigger button. When activated the instrument drives the plunger towards the distal end of the instrument which causes the needle in the disposable needle holder on the plunger to pierce the patient's skin and create a drop of blood sufficient for testing.
As suggested by Levin et al., in Col. 2, lines 17-19, there are conventional disposable needle holders available on the market for use with the Levin et al. instrument, e.g., a MONOLET.TM. lancet assembly. However, conventional lancet assemblies are difficult to handle and manipulate when loading the instrument and have shields mounted directly on their needles that are difficult to remove from the needle and may cause damage to the needle when being removed. In addition, conventional needle holders are manufactured using insert molding, which is expensive and makes it difficult to inspect the assembly/needle and precisely place the needle within the needle holder to control penetration depth.